Boundary-value problems in cosmological dynamics

TL;DR

This paper presents a least action principle-based method for reconstructing cosmic density and velocity fields from galaxy distribution and peculiar velocity data, aiding understanding of dark matter and mass-light relations.

Contribution

It introduces a novel dynamical reconstruction approach using a least action principle to analyze cosmological data sets.

Findings

Reconstructed velocity fields from galaxy distribution data.

Constraints on dark matter properties derived from data comparison.

Insights into the mass-light relation in the Universe.

Abstract

The dynamics of cosmological gravitating system is governed by the Euler and the Poisson equations. Tiny fluctuations near the big bang singularity are amplified by gravitational instability into the observed structure today. Given the current distribution of galaxies and assuming initial homogeneity, dynamical reconstruction methods have been developed to derive the cosmic density and velocity fields back in time. The reconstruction method described here is based a least action principle formulation of the dynamics of collisionless particle (representing galaxies). Two observational data sets will be considered. The first is the distribution of galaxies which is assumed to be an honest tracer of the mass density field of the dark matter. The second set is measurements of the peculiar velocities (deviations from pure Hubble flow) of galaxies. Given the first data set, the reconstruction method recovers the associated velocity field which can then be compared with the second data set. This comparison constrains the nature of the dark matter and the relation between mass and light in the Universe.